Raspberry Pi Bare Bones: Difference between revisions

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     .org 0x80000
-// Entry point for the kernel. Registers are not defined as in AArch32.
+// Entry point for the kernel. Registers:
+// x0 -> 32 bit pointer to DTB in memory (primary core only) / 0 (secondary cores)
+// x1 -> 0
+// x2 -> 0
+// x3 -> 0
+// x4 -> 32 bit kernel entry point, _start location
 _start:
-    // read cpu id, stop slave cores
-    mrs     x1, mpidr_el1
-    and     x1, x1, #3
-    cbz     x1, 2f
-    // cpu id > 0, stop
-:  wfe
-    b       1b
-:  // cpu id == 0
     // set stack before our code
-    ldr     x1, =_start
+    ldr     x5, =_start
-    mov     sp, x1
+    mov     sp, x5
     // clear bss
-    ldr     x1, =__bss_start
+    ldr     x5, =__bss_start
-    ldr     w2, =__bss_size
+    ldr     w6, =__bss_size
-:  cbz     w2, 4f
+:  cbz     w6, 4f
-    str     xzr, [x1], #8
+    str     xzr, [x5], #8
-    sub     w2, w2, #1
+    sub     w6, w6, #1
-    cbnz    w2, 3b
+    cbnz    w6, 3b
     // jump to C code, should not return

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